This boils down to the same reason not all laptops are the same. Or not all cars are the same. All lasers that are used in the United States must be approved by the Food and Drug Administration (FDA), but they are of varying quality and offer different levels of performance and features. The Allegretto Wavelight EX500 is the most recent device to get approval for LASIK. In the FDA clinical trials it achieved better outcomes than any laser tested previously. It has also been granted the broadest range of prescription approvals by the FDA. It is the 9th laser platform that Dr. Robbins in his experience the best so far by a wide margin.